Replaceable roller bogie for document feeding apparatus

ABSTRACT

A replaceable roller bogie for a single sheet feeder includes pre-feed and separation rollers mounted on a frame which also has a frame positioning lever thereon. Roller drive gears are mounted between spaced plates on the frame and include a pre-feed roller clutch gear with elastomeric teeth which is mounted in slots on the frame which limit motion travel of the clutch gear to prevent over engagement of gear teeth on the clutch gear with gear teeth on the pre-feed roller drive gear. The replaceable bogie is pivotally supported on the sheet feeder and held in place by a manually operable release and latch mechanism.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] None.

BACKGROUND OF THE INVENTION

[0002] The present invention relates generally to the art of documentprocessing equipment such as scanners, printers, facsimile machines andcombination devices which use single sheet feeders to pick single sheetsof media to be processed from a stack thereof. Such equipment includessheet moving rollers, belts or wheels and, in particular, the sheetfeeders with which the present invention is concerned employ both apre-feed roller and a separation roller spaced downstream from thepre-feed roller. A stack stop is positioned to be moved into and out ofthe path of sheet movement between the rollers. Worn or otherwisedamaged rollers in such equipment occasionally require replacementnecessitating a service call and attendant expense. It is accordinglydesirable to provide a modular single sheet feeder which can be easilyassembled at the factory and which also has easily replaceable rollerswhich can be serviced by the user without the necessity to involve askilled service technician.

SUMMARY OF THE INVENTION

[0003] The present invention therefore provides a roller bogie for asingle sheet feeder, said bogie comprising:

[0004] a) a frame;

[0005] b) a pre-feed roller rotatably supported on said frame;

[0006] c) a single sheet separation roller rotatably supported on saidframe; and

[0007] d) roller drive gears rotatably mounted on said frame, and

[0008] e) axially aligned spaced bogie support bearings on said frame,said bearings being configured for reception in spaced bogie supports ina single sheet feeder.

[0009] The present invention further provides a method of replacingsheet transport rollers in a sheet feeder comprising the steps of:

[0010] a) providing a roller bogie having sheet transport rollersthereon,

[0011] b) mounting said bogie on bogie support structure in a sheetfeeder, said support structure including a latch for securely holdingsaid bogie on said support structure;

[0012] c) releasing said latch and removing said bogie from said sheetfeeder apparatus;

[0013] d) replacing said bogie with a new bogie; and

[0014] e) closing said latch.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015]FIG. 1 is a perspective view of a single sheet feeder module whichincludes a media input tray shown partly in section, a modular rollersupport assembly, and a removable roller bogie.

[0016]FIG. 2 is a top plan view of the sheet feeder module.

[0017]FIG. 3 is a cross sectional elevation taken at line 3-3 on FIG. 2.

[0018]FIG. 4 is an exploded perspective view of the bogie.

[0019]FIG. 5 is a plan view of the bogie.

[0020]FIG. 6 is a cross sectional elevation of the bogie taken at line6-6 on FIG. 5 showing a stack damper on the bogie.

[0021]FIG. 7 is a right side elevation of the bogie.

[0022]FIG. 8A is a cross sectional elevation of the bogie taken at line8-8 on FIG. 5 showing the gear cluster and disengaged pre-feed rollerclutching gear.

[0023]FIG. 8B is a cross sectional elevation of the bogie like FIG. 8Ashowing the engaged position of the pre-feed roller clutching gear.

[0024]FIG. 9 is a plan view of the modular roller support assembly andbogie removed from the sheet feeder module.

[0025]FIG. 10 is a perspective view of the modular roller supportassembly.

[0026]FIG. 11 is a cross sectional elevation of the modular rollersupport assembly taken at line 11-11 on FIG. 9 showing the bogie liftinghandle.

[0027]FIG. 12 is a cross sectional elevation taken at line 12-12 on FIG.9 showing a bogie support load arm.

[0028]FIG. 13 is a cross sectional elevation taken at line 13-13 on FIG.9 showing the bogie latch and the stack stop.

[0029]FIG. 14 is a cross sectional elevation taken at line 14-14 on FIG.9 showing the main clutch gear disengaged from the separation rollerdrive gear.

[0030]FIG. 15 is a cross sectional elevation taken at line 15-15 on FIG.9 showing the follower engagement with the swing arm.

[0031] FIGS. 16A-16E show five positions of the bogie and stack stop ascontrolled by different positions of a cam follower moved by a cam andby a swing arm.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0032] The modular sheet feeder 10 seen in the perspective view in FIG.1 is a separate unit of a document processing apparatus which includes adocument processing module (not shown) such as a printer, scanner,facsimile machine or copier or combination of any of the foregoing. Thesheet feeder module 10 is affixed to the document processing module (notshown) for feeding individual sheets from the top of a stack thereof tosheet transporting mechanism in the document processing module.

[0033] The sheet feeder module 10 is comprised of an input tray, notshown, that attaches to input frame 20 having a stack support surface 22and spaced sides 24, 26 in the form of upstanding walls which define asheet transport path for moving individual sheets from the top of astack supported on a stack support surface 22 from left to right as seenin FIG. 1. The side wall 24 includes a shaft mounting cradle having anon-circular gate 28 and an integrally formed spring mounting post 30for purposes which will be described. The other side wall 26 is providedwith a bushing aperture 32 located in a motor support plate 34 attachedby suitable fasteners to the wall 26. A reversible electric step motor35 is supported on the motor support plate 34 which, with the wall 26,defines a housing for the motor and motor output gear (not shown).

[0034] The input frame 20, which may be of molded plastic as isconventional, includes a stack retard wall 36 which is angled upwardlyand away from the stack support surface 22 and with a retard pad 38positioned for engagement with the arcuate surface of a single sheetseparation roller 90 and with a pad 40, preferably of cork, forengagement with a sheet pre-feed roller 80. As used herein, the term‘roller’ includes single and multiple rollers and spaced or adjacentcoaxially mounted wheels and equivalents for moving single sheets ofmedia such as moveable belts trained around spaced rollers.

[0035] A replaceable roller bogie comprising a frame 50 formed of spacedside members or plates 52, 54 joined by a cross piece 60 support apre-feed roller 80 and a single sheet separation roller 90 downstream ofthe pre-feed roller 80. Side plate 54 has an integrally formed tail orlever arm 56 which extends generally parallel to a line connecting thecenters of rotation of the pre-feed roller 80 and single sheetseparation roller 90. The side plates 52, 54 include bearing apertures62, 64 for a pre-feed roller support shaft and bearing apertures 66, 68for a separation roller support axle 92. A gear retainer plate 70 ismounted on and spaced from side plate 54 by spacing posts 74 andfasteners 76. A pre-feed roller clutch gear shaft slot 58 in side plate54 aligns with a pre-feed roller clutch gear shaft mounting slot 72 inthe gear retainer 70.

[0036] The sheet pre-feed roller 80 is supported on a shaft 81 whoseends are received in the apertures 62, 64 in the side plates 52, 54,respectively. As is conventional, the pre-feed roller has an elastomericsurface or a surface texture suitable for engaging the top surface of asheet to be removed from the stack. Similarly, the single sheetseparation roller 90 is supported on an axle 92 the ends of which arereceived in the bearing apertures 66, 68 in the side plates 52, 54. Insheet transporting position, the separation roller 90 forms a sheetseparation nip with a surface of the retard pad 38. The separationroller axle 92 has spaced support bearings 94, 96 thereon for a purposeto be described and a separation roller drive gear 98 is also mounted onthe axle 92 for driving the separation roller 90. A plurality ofintermediate gears 102, 104 may be provided to transmit power from therotating separation roller 90 to rotate the pre-feed roller 80 through apre-feed roller clutch gear 110 which preferably has elastomeric teethpermanently engaged with the separation roller drive gear 98 or with oneof the intermediate gears. The clutch gear 110 is supported on a shaft,the ends of which are received in the slots 58, 72 which are preferablyarcuate and are centered on the axis of rotation of a drive orintermediate gear which is continually engaged with the clutch gear 110.

[0037] A stack damper 120 is freely rotatable on the pre-feed rollersupport shaft 81, the stack damper having a surface which extends in thedownstream direction of sheet movement from the pre-feed roller 80parallel to the surface of a stack of media sheets on the supportsurface 22. The stack damper 120 is heavy enough to prevent buckling ofthin sheets between the pre-feed roller 80 and the separation roller 90and is free to pivot upwardly by sheet contact, particularly with heavysheets, until it engages a stop surface on the frame such as the crosspiece 60 as seen in FIG. 6. The roller frame 50 thus supports thepre-feed roller 80, single sheet separation roller 90, gears and stackdamper 120, if provided, which together comprise a replaceable bogiewhich is supported by a modular roller support and drive assembly 200 tobe described.

[0038] The modular roller support and drive assembly 200 is comprised ofa shaft 201 received in axially aligned shaft supports in the spacedside walls 24, 26 of the input tray 20. One of the shaft supportscomprises the bushing aperture 32 into which one end of the shaft isinserted as the other end of the shaft, having a part non-circularconfiguration, is rotated to the appropriate position to be dropped intothe other support through the non-circular shaft mounting slot 28. Theshaft also has a transversely extending spring arm 202 non-rotatablyaffixed to the shaft, the arm 202 having a spring retainer or boss 204protruding therefrom. A biasing member, preferably a tension spring 206,is connected between the spring retainer 30 on the side of the inputtray and the boss 204 on the spring arm 202. The spring 206 passes overthe center axis of the shaft 201 as the spring is tensioned.

[0039] The replaceable bogie is supported between a pair of spaced bogiesupport load arms 210, 212 non-rotatably affixed to the shaft 201. Thebogie support arms preferably also include spaced axially alignedsupport hubs 214 for supporting a stack stop link 252. The load arms210, 212 also preferably have spaced transversely extending stack stopguides 216 thereon and are provided with aligned bogie support aperturesor slots 218, 220 in which the spaced bearings 94, 96 on the separationroller axle 92 are received to support the removable bogie on themodular roller support and drive assembly 200. A bogie retention latch230 having a release button 232 and spaced latch hooks 234 is pivotallymounted between the bogie support arms 210, 212, the latch being biasedto closed position by a bogie latch spring 236 seated between the bogielatch button and a transverse brace which extends between and isconnected to the load arms 210, 212. The latch hooks 234 engage thebogie support arms when the latch is closed to avoid clamping of thelatch hooks onto the bearings 94, 96 of the separation roller axle 92.

[0040] A bogie lifting handle 240 is preferably also provided, thehandle 240 being non-rotatably affixed to the support shaft 201. Thelifting handle is biased to a downward position by a spring 242 engagedwith a seat on the load arm 210 so that lifting of the handle 240 firstcompresses the spring 242 before lifting the load arms 210, 212 andattached bogie. The compression spring 242 also biases the bogiedownwardly through contact of the end of the handle 240 with the uppersurface of the bogie frame providing the force on the pre-feed roller 80in the media feed position and urging the frame tail or lever arm 56upwardly against a cam surface of a follower 260 to be described whenthe follower has lifted the bogie to the up positions. The liftinghandle 240 and tension spring 206 are designed with over center geometryso that the spring 206 will bias the bogie downwardly for sheet feedingand will hold the handle and bogie in the lifted position to facilitateremoval of jammed sheets and inspection of the paper path.

[0041] A stack stop 250 comprising a substantially rectangular platewhich is vertically guided between the stack stop guides 216 ispivotally connected to and extends downwardly from a stack stop link 252between the pre-feed roller 80 and single sheet separation roller 90.The stack stop link 252 is pivotally attached to and supported betweenthe spaced load arms 210, 212 such that the stack stop 250 is movableinto and out of the path of movement of a media sheet downstream of thepre-feed roller 80 and upstream of the single sheet separation roller90. A downwardly extending leg 256 is integrally formed on a stack stoplink for engagement with a follower 260 to lift and lower the stack stop250.

[0042] As seen best in FIG. 16, the follower 260 having a pivot aperture262 therein is pivotally mounted on a follower support post 222 receivedin the aperture 262, the post extending outwardly from the load arm 212in a direction parallel to the axis of the support shaft 201. Thefollower 260 has a point 264, a cylindrical first cam surface 266 (FIG.16A) which engages the bogie tail lever arm 56 as the follower 260pivots on its support post to partly raise the bogie and pre-feed roller80 supported thereon relative to the stack support surface 22 in thetray 20 when a stack of sheets is to be inserted against the stack stop250. The follower 260 also has a second cam surface 268 which engagesthe leg 256 on the stack stop link 252 for raising and lowering thestack stop into and out of sheet blocking position. A third cam surface270 (FIG. 16C) on the follower 260 is provided for engagement with thebogie tail lever arm 56 and is used for test purposes not relevantherein when the single sheet feeder module is not installed on thedocument processing module. The follower 260 also includes an axiallyprotruding portion in the form of a pin 272 for a purpose to bedescribed.

[0043] The modular roller support and drive assembly 200 also includes aswing arm 280 axially supported on the shaft 201 for rotation relativeto the shaft 201 by spaced swing arm supports 284, 286. A power inputgear assembly 290 having axially spaced gears 291 affixed to oppositeends of a sleeve 292 is mounted on the support shaft 201. One of theaxially spaced gears 291 receives input power from an automaticdirection finding gear drive (not shown) driven by the motor 35. Theother of the axially spaced gears 291 on the input gear assembly 290 iscontinuously engaged with a clutch gear 294 supported on the swing arm280. A drag spring 295 for the clutch gear 294 is also provided. Apocket 296 seen in FIGS. 16(3) in the side face of the swing arm 280receives the pin 272 on the follower so that rotation of the swing armon shaft 201 lifts the follower 260 when the input gear assembly 290 isrotated in the reverse direction of rotation by the motor 35. A motionlimit hook 300 is also integrally formed on the swing arm 280 forengagement with the protruding end of the separation roller axle 92 toprovide over-engagement protection between the teeth of the main clutchgear 294 and the separation roller drive gear 98 and to restrain liftingof the bogie frame 50.

[0044] A rotary cam Geneva 310 is also affixed to the input gearassembly 290 and is positioned on the remote side of the swing arm 280from the gears 291 and in alignment with the follower 260 so that thepoint 264 on the follower engages a cylindrical surface of the cam andis permitted to enter an aperture 312 in the form of a slot 312 in thecylindrical surface of the cam 310 when the cam rotates in the forwardor counterclockwise direction as seen in FIGS. 16(1). Reverse rotationof the input gear assembly 290 causes the cam 310 to lift the point 264from the slot aperture 312 to raise the bogie and lower the stack stop250 for insertion of a new stack of media sheets.

[0045] The swing arm 280 and input gear assembly 290 including the camGeneva 310 which are all rotatably supported on the shaft 201 areretained on the shaft by a retainer 320 suitably affixed to the shaft toaxially position one of the input gears 291 in alignment with the motoroutput gear (not shown) and the other gear 291 is positioned forengaging the clutch gear 294 supported on the swing arm 280. As seen inFIG. 10, the retainer 320 has an arcuate, preferably cylindrical,surface 322 adjacent to the input gear 291 in a position such that thecylindrical surface 322 will be engaged by a motor output gear supportwhich moves the motor output gear (not shown) into and out of engagementwith the input gear 291 and thus prevents over engagement of the motoroutput gear and the input gear 291. The retainer 320 may be held inposition on the shaft 201 by a snap spring seated in a properly axiallypositioned circumferential groove on the shaft 201 or by any othersuitable means. A split sleeve 330 made of resilient plastic is snappedonto the other end of the shaft 201 adjacent the bogie lifting handle240 to provide proper positioning of the lifting handle 240.

[0046] Operation

[0047] A stack of media sheets is inserted into the sheet feeder beneaththe pre-feed roller 80 which is initially positioned at a distance abovethe stack support surface 22 to permit stack insertion until the leadingedge of the stack engages the stack stop 250. Application of input powerin the forward direction to the input gear assembly 290 then rotates theGeneva cam 310 and aperture 312 to a position which permits the followerfinger 264 to drop into the cam aperture 312. Continued forward rotationof the motor then lifts the stack stop 250 and drops the bogie androller 80 into sheet transporting position. The pre-feed roller 80 isunder driven relative to the separation roller 90 which subsequently isunder driven with respect to the sheet moving rollers in the documentprocessing module (not shown) such that sheets are pulled through thefeeder. In addition, both the pre-feed roller 80 and the separationroller 90 are clutch driven to allow them to be over driven by the mediasheet. The pre-feed roller drag spring 84 places drag on the pre-feedroller drive gear to permit dwell to be built up in the pre-feed roller80. The pre-feed roller 80 is under driven so that dwell can beaccumulated during advancement of the sheet of media, the dwell thenbeing consumed after the trailing edge of one sheet leaves the pre-feedroller 80. This dwell then allows the pre-feed roller to remainstationary so that a second sheet will also remain stationary until thetrailing edge of the first sheet has just left the nip defined betweenthe separation roller 90 and the tray 20.

[0048] Since the separation roller 90 must be under driven relative tothe downstream document processing rollers (not shown) the separationroller 90 needs to be clutched in an overdrive situation to preventabnormally high back tension from the sheet feeder module andunnecessary parasitic torque losses in the drive system caused by asheet of paper pulled by the downstream document processing modulerollers. The clutch gear 294 for the separation roller 90 thereforeneeds to engage when the bogie is in the down position. Also, the stackstop 250 must be in the up position whenever the rollers 80, 90 aredriven to transport a sheet of media. Conversely, the clutch gear 294for the separation roller 90 is disengaged when the bogie is up, thestack stop is down, and the system is dormant. The separation rollerclutch gear 294 also allows the separation roller to free wheel when thesheet is being pulled down downstream by the document processing modulerollers.

[0049] The follower finger 264 is always urged against the cylindricalsurface of the Geneva cam 310 due to bias by the tail lever arm 56 onthe bogie frame 50 on the cam surface 266 of the follower 260. Althougha compression spring 242 engaged with the lifting arm provides thisbias, various alternatives can easily be envisioned by those skilled inthe art. The point on the end of finger 264 is therefore urged into theaperture 312 whenever the aperture rotationally passes in the forwarddirection past the finger 264 but the aperture in the cam 310 is curvedto prevent entry of the point into the aperture when the cam 310continues to rotate in the same direction after the finger 264 hasexited the aperture 312. This provides four stable operational positionsof the follower:

[0050] 1. Stack Insertion or Up-Up—The pre-feed roller 80 is spaced fromthe input tray and the follower 260 and protruding pin 272 are in the upposition and the point 264 engages the cylindrical surface of the cam310 anticipating passage of the slot as seen in FIG. 16A(1). Thefollower 260 is upwardly biased by the bogie tail lever arm 56. Thecoefficient of friction between the engaged surfaces of the follower andlever arm must be low enough to ensure that the lever arm urges thefollower point 264 toward the surface of the cam 310. The swing arm 280is also in the up position as seen in FIG. 16A(2 and 3) and a lower wallof swing arm pocket 296 is engaged with the pin 272.

[0051] 2. Up-Down—The pre-feed roller 80 is still spaced from the inputtray since the follower 260 is in the up position but the point 264 hasmoved into the aperture 312 as seen in FIG. 16B(1). It is to be notedthat the point 264 enters the aperture 312 only when the cam is rotatedin the reverse direction (counterclockwise as seen in FIG. 16). Thefirst cam surface 266 on the follower allows the follower to maintain ina stable up-down state without jumping to one of the followingpositions. The swing arm 280 has commenced downward movement as seen inFIG. 16B(2 and 3) and an upper wall of the pocket 296 now engages thepin 272.

[0052] 3. Operational State—This position seen in FIGS. 16C(1-3) is usedto pre-feed a document from the input stack and present it to theseparation nip and then drive the sheet to the scanning region of theapparatus. The pre-feed roller 80 rests on top of the input stack ofmedia and is downwardly biased with sufficient sheet picking force bythe handle 240. The follower and stack stop are in the same position asin the down states but there is clearance between the follower surface270 and the tail lever arm 56. This allows all of the force from thelifting handle 240 to load the pre-feed roller against the input stack.The swing arm is down and engaged and the bogie clutch gear is engaged.Rotational power input then rotates the rollers 80, 90 in the forwarddirection.

[0053] 4. Down-Up—This position is used when testing the modular rollersupport and drive assembly 200. The pre-feed roller 80 is in the downposition as cam 310 is rotated in the reverse direction and the followerpoint 264 has entered the aperture 312 in the cam 310 due to engagementof the tail lever arm 56 with the first cam surface 266 of the followerpushing the point up into the aperture 312 as seen in FIG. 16D(1). Theswing arm 280 is in the up and disengaged position as seen in FIGS.16D(2 and 3) when the input is rotating in the reverse (clockwise)direction. There is enough space in the pocket 296 to allow the swingarm to rotate down into the engaged position if the input power isapplied in the forward (counterclockwise) direction.

[0054] 5. Down-Down—The pre-feed roller 80 and follower 260 are down andthe point 264 is ready to enter the aperture 312 in the cam Geneva asseen in FIG. 16E(1). The swing arm 280 is also in the down position asseen in FIGS. 16E(2 and 3).

[0055] The second cam surface 268 on the follower engages the leg 256 ofthe stack stop link 252 to raise the stack stop 250 when the followerrotates to the down position seen in FIGS. 16D and E. When the follower260 rotates to the up position, the stack stop link and stack stop arelowered as seen in FIGS. 16A and B.

[0056] Engagement of the follower pin 272 by the walls of the swing armpocket 296 ensures that when the follower 260 is in the up position thebogie is also up and the stack stop 250 is in the down position and themain clutch gear 294 on the swing arm is not engaged with the separationroller drive gear 98. Thus, the system is in “neutral” so that the inputgear assembly 290 can rotate indefinitely in the reverse directionwithout engagement of the drive train for the rollers 80, 90.

[0057] The drag spring 295 for the main clutch gear 294 gives the clutchgear a propensity to engage when rotating in the forward direction andthe motion and the impetus to disengage when the clutch gear rotates inthe reverse direction. This impetus is transferred to the pin 272 on thefollower by the surfaces of the pocket 296 on the swing arm. There isadequate spacing between the pocket surfaces such that some over travelof the swing arm 280 is permitted for the overrunning clutching purposespreviously explained. The surfaces of the pocket 296 are angled suchthat they rotate the follower about its pivotal support post 246 withthe maximum amount of engagement of the point 264 with the Geneva cam310.

[0058] The stack damper 120 on the bogie frame 50 is preferably made ofplastic and has a weight heavy enough to constrain thin media sheetsdriven by pre-feed roller 80 to prevent buckling in the area between thepre-feed roller 80 and the separation roller 90, yet light enough toprevent it from buckling between the pre-feed roller 80 and stack damper120. The stack damper 120 is also stopped in its upward travel to imparta slight bend to thick media sheets during sheet movement imparted bythe pre-feed roller 80. The stack damper 120 falls after each sheetpasses to beat down subsequent sheets of media that may be climbing upthe inclined retard wall 36 reducing the tendency for more than just afew sheets to thereafter be driven over the top of the wall 36. Thestack damper 120 rests by gravity on top of the top sheet of media. Thebottom surface of the stack damper 120 is tangential to the outer drivesurface of the pre-feed roller 80 to ensure that the surface of thestack damper is always in flat contact with the top sheet of the inputstack regardless of the height of the input stack. The physicalengagement of the stack damper 120 with a very stiff sheet to slightlybend it thus prevents it from moving straight from the input stack overthe crest of the retard wall 36, scrubs off additional sheets fromclimbing over the top edge of the retard wall 36 and initiates properform to a stiff sheet by providing a bend orthogonal to the direction ofmovement of the sheet. This eliminates sheet curl and otherdiscontinuities that may exist in an axis parallel with the direction ofmovement of the sheet that can disturb single sheet separation.

[0059] The modular roller support and drive assembly 200 can easily beassembled to and removed from the tray 20 by detaching the spring 206.The support shaft 201 can then be rotated to the proper position so thatit can be removed from its supports in the side walls of the tray 20.The mounting of the entire roller support and drive assembly 200 on asingle support shaft 201 enables accurate alignment, loading andpositioning of the various structural pieces mounted on the shaft.

[0060] The pre-feed roller clutch gear 110 is preferably made ofelastomeric material or has elastomeric teeth thereon for quietoperation. The clutch gear 110 is supported on an axle received in slots58, 72, the bottom saddle of which prevents over engagement of theclutch gear with the pre-feed roller drive gear 82. When the pre-feedroller 80 is over driven, the clutch gear 110 moves upwardly until itsteeth disengage from the pre-feed roller drive gear 82. The slots areangled or preferably arcuate such that the clutch gear never disengagesfrom the intermediate drive gear with which it is engaged. The use ofelastomeric teeth on the clutch gear 110 has been found to significantlyreduce objectionable clicking noises created when clutching gears madeout of hard plastic materials are moved into engagement with the drivengear.

[0061] Persons skilled in the art will also appreciate that variousadditional modifications can be made in the preferred embodiment shownand described above and that the scope of protection is limited only bythe wording of the claims which follow.

1. A roller bogie for a single sheet feeder, said bogie comprising: a) aframe; b) a pre-feed roller rotatably supported on said frame; c) asingle sheet separation roller rotatably supported on said frame; and d)roller drive gears rotatably mounted on said frame, and e) axiallyaligned spaced bogie support bearings on said frame, said bearings beingconfigured for reception in spaced bogie supports in a single sheetfeeder.
 2. The roller bogie of claim 1, wherein said frame is comprisedof a pair of spaced side plates and at least one cross pieceinterconnecting said side plates, said pre-feed roller and saidseparation roller being supported between said side plates for rotationabout parallel axes.
 3. The roller bogie of claim 2, wherein said bogiesupport bearings are coaxial with said separation roller.
 4. The rollerbogie of claim 3, further comprising a bogie positioning lever extendingfrom said frame in a direction generally parallel to and spaced from aline connecting the axes of rotation of said rollers.
 5. The rollerbogie of claim 3, further comprising a gear retainer affixed to one ofsaid side plates, said gears being mounted between said gear retainerand said one side plate.
 6. The roller bogie of claim 5, furthercomprising a pre-feed roller drive gear connected to said pre-feedroller and a pre-feed roller clutch gear engageable with said pre-feedroller drive gear and wherein rotary power delivered in a forwarddirection to said gears causes said clutch gear to engage with saidpre-feed roller drive gear to rotate said pre-feed roller in a sheetdelivery direction.
 7. The roller bogie of claim 6, wherein saidpre-feed roller clutch gear is mounted on an axle received in slots insaid gear retainer and said one side plate, said slots having seatswhich are engaged by said axle to prevent over engagement of said clutchgear and said pre-feed roller drive gear.
 8. The roller bogie of claim7, wherein rotary power delivered in a reverse direction to said gearscauses said clutch gear to disengage from said pre-feed roller drivegear.
 9. The roller bogie of claim 8, wherein said pre-feed roller isconnected by said gears to said separation roller such that saidpre-feed roller is under driven in said forward direction at a surfacespeed slower than the surface speed of said separation roller.
 10. Theroller bogie of claim 9, further comprising a drag spring frictionallydragging between said side plate and said pre-feed roller to build updwell.
 11. The roller bogie of claim 10, further comprising mountingslots in said gear retainer and said one side plate, said clutch gearhaving axial supports received in said slots, said slots extending in adirection such that said clutch gear disengages from said pre-feedroller drive gear during rotation of said gears in a reverse directionand engages with said pre-feed roller drive gear during rotation of saidgears in a forward direction.
 12. The roller bogie of claim 11, whereinsaid slots are configured such that said clutch gear is continuouslyengaged with another one of said gears.
 13. The roller bogie of claim12, wherein said clutch gear has elastomeric teeth thereon.
 14. Theroller bogie of claim 9, further comprising at least one intermediategear engaged with said separation roller drive gear and with saidpre-feed roller clutch gear.
 15. The roller bogie of claim 1, furthercomprising a stack damper pivotally mounted for rotation about the axisof rotation of said pre-feed roller, said stack damper having a surfacewhich extends in the downstream direction of sheet movement from saidpre-feed roller parallel to the surface of a stack of media sheets. 16.The roller bogie of claim 15, wherein said stack damper has a weightheavy enough to prevent buckling of thin media sheets, said stack stopbeing restrained in upward movement by said frame to impart a slightbend to thick media sheets during sheet movement imparted by saidpre-feed roller.
 17. A method of replacing sheet transport rollers in asheet feeder comprising the steps of: a) providing a roller bogie havingsheet transport rollers thereon, b) mounting said bogie on bogie supportstructure in a sheet feeder, said support structure including a latchfor securely holding said bogie on said support structure; c) releasingsaid latch and removing said bogie from said sheet feeder apparatus; d)replacing said bogie with a new bogie; and e) closing said latch. 18.The method of claim 17, wherein said latch is released by depressing arelease button to open a support aperture on said bogie support andinserting support structure on said bogie into said aperture andreleasing said button to hold said bogie in operative position in saidsheet feeder.
 19. The method of claim 18, wherein said bogie ispivotally moveable in said support aperture with respect to said sheetfeeder.
 20. The method of claim 19, further comprising the step ofmoving said bogie and bogie support on said sheet feeder to expose saidbogie for replacement.
 21. The method of claim 20, wherein said bogieand bogie support are pivotally moved with respect to said sheet feederto expose said bogie for replacement.
 22. A sheet feeder having an inputgear affixed to a shaft, said input gear being engageable with a motordriven output gear for transmitting bi-directional input power deliveredby said motor driven output gear to at least one sheet feeder roller, amotion limiter having an arcuate surface mounted on said shaft proximatesaid input gear for engagement of said arcuate surface with a pivotalmotor output gear support to prevent over engagement of teeth on saidoutput gear and said input gear.
 23. The sheet feeder of claim 22,wherein said motion limiter comprises an input gear retainer forretaining said input gear in desired axial position on said shaft. 24.The sheet feeder of claim 23, wherein said motion limiter isnon-rotatably affixed to said shaft alongside said input gear.
 25. Thesheet feeder of claim 24, wherein said arcuate surface is cylindrical.